1. Field of the Invention
The present invention relates to an information terminal apparatus having a small, light and thin housing structure such as a mobile phone and a personal digital assistant including a flat-panel display (FDP) such as a liquid-crystal display (LCD) and which can be driven by batteries and a portable television receiver with a flat-panel display.
2. Description of the Related Art
As an information terminal apparatus including a flat-panel display such as a liquid-crystal display and which can be driven by batteries, various kinds of devices such as a mobile phone, an information terminal apparatus and a portable television broadcasting receiver with a flat-panel display have been created so far and are now commercially available on the market. As a mechanism for attaching and holding a battery pack to accommodate therein batteries, it has been customary to use a structure to insert a battery pack into a battery pack compartment from one side wall of the apparatus, a battery cover being attached to the battery pack compartment.
For example, FIG. 1 shows an example of an information terminal apparatus according to the related art. A monitor apparatus, generally depicted by reference numeral 100 in FIG. 1 is an information terminal apparatus including a display. The monitor apparatus 100 accommodates a battery pack 101 into the nearby portion of the center of a rear wall 100d and a battery cover 104 is attached to the battery pack 101. The monitor apparatus 100 further includes a U-shaped stand 110 attached to a rotary shaft (not shown) so as to become openable and closable (rotatable) freely about the rotary shaft. When this monitor apparatus 100 is in use, the stand 110 is pulled out of a stand compartment groove portion (not shown) and stretched with a predetermined angle to enable the monitor apparatus 100 to rise to the erect position.
FIG. 2 shows the monitor apparatus 100 with the battery cover 104 being removed. As shown in FIG. 2, when the battery cover 104 is removed from a rear wall 100d, a battery pack compartment recess 103 is formed in the inside of the rear wall 100d and the battery pack 101 is inserted into the battery pack compartment recess 103, the battery cover 104 being attached to the battery pack compartment recess 103 from above. In FIG. 2, reference numeral 102 denotes each cell of the batteries accommodated within the battery pack 101.
When it is intended to realize an information terminal apparatus with multifunction, in order to solve a problem of freedom in design, there has been proposed an information terminal apparatus having a structure in which a battery pack compartment is formed at, for example, the center of the rear wall portion of the apparatus to accommodate therein the battery pack (see cited patent reference 1).
[Cited Patent Reference]:
Japanese laid-open patent application No. 2002-169630
Batteries for use in driving the information terminal apparatus and the like as mentioned above are typically secondary batteries such as lithium ion cells and fuel cells such as hydrogen-occluded fuel cells. When these batteries are charged and discharged, they inevitably generate heat. When temperature of the secondary battery rises due to the thus generated heat or when the secondary battery is kept in the high temperature state, this becomes a significant factor to promote an electric capacity charging recovery rate of battery to be lowered.
At present, when a battery-driven information terminal apparatus is realized, a flat-panel display consumes a large amount of electric power, and a power consumption of the whole of the system of the information terminal apparatus is large because a CPU (central processing unit) and a DSP (digital signal processor) used therein become higher in performance and are driven at higher frequencies. As a consequence, the whole of the information terminal apparatus needs very large electric power. In order for the information terminal apparatus including at least the above-described flat-panel display to browse contents such as television broadcasting data having a large amount of data and which requires high brightness, such apparatus needs a battery pack mounted thereon to supply a large amount of electric current.
Problems that encountered with the information terminal apparatus when the related-art battery pack is in use are heat generated from cells when the cells are charged and discharged and heat generated from respective assemblies and elements provided within the housing including the battery pack. While most of electronic assemblies have operation guaranteeing temperature of approximately 70° C., the cell located within the battery pack is one of the parts of the assemblies of the information terminal apparatus that should be held at temperature close to ordinary temperature.
It has been customary that the operation guaranteeing temperature and the life guaranteeing temperature of the cell are set to 45° C. when it is charged and set to 60° C. when it is discharged. Having considered these aspects, it is to be noted that the package of the battery pack should be kept at temperature slightly lower than those operation guaranteeing temperature and life guaranteeing temperature (ideal temperature at which the battery pack is in use is approximately 25° C. Therefore, the package of the battery pack should be kept at this proper temperature. Otherwise, the life span of the battery is decreasing progressively and finally the battery itself becomes unable to function.
As methods for solving these problems, there are considered various methods such as partial heat transferring methods using a heat sink and a heat pipe made of metal parts, an air heat transferring method in which an apparatus includes a metal housing to conduct heat to the whole of the metal housing, a forced-cooling method using a housed fan, a water-cooling cooling method using a coolant, etc.
Of these methods, the metal assembly becomes an unnecessary antenna required when the information terminal apparatus is an information terminal apparatus capable of making wireless communication. Since this metal assembly causes significant wireless communication interference, this metal assembly is difficult to use and is disadvantageous from a weight standpoint. This applies for the case of the water-cooling cooling method using the coolant as well. Furthermore, since the fan generate undesired sounds, it is not preferable to use it in a portable device, and it is not easy to effectively mount the fan into a small, light and thin housing.
As an information terminal apparatus that receives a remarkable attention from a standpoint of heat problem at present, there are roughly classified three types of information terminal apparatus such as a housing type high-speed communication apparatus such as a notebook type PC (personal computer) and a server, an apparatus such as a television receiver needing large electric power to display images and a wireless communication apparatus such as a mobile phone designed so as to consume lesser electric power and which can be driven by batteries. Therefore, heat should be transferred from the battery pack to the outside while all problems, such as removal of undesired sounds, light and thin information terminal apparatus and highly-sensitive wireless communication, which encountered with these three types of the information terminal apparatus, should be solved.
However, although the information terminal apparatus of the type to house therein the battery pack that has been described in the cited patent reference 1 can improve freedom in designing the information terminal apparatus when this information terminal apparatus mounts the battery pack, improvement of heat transferring effect of the battery pack is not taken into consideration. As a result, since the battery pack is accommodated within the housing of the information terminal apparatus, it is unavoidable that heat generated from the battery, heat generated from the display and heat generated from an electric circuit such as an IC (integrated circuit) are confined within the housing of the information terminal apparatus.
FIG. 3 is a cross-sectional view taken along the line A—A in FIG. 2 and shows the marginal portion of the battery pack portion. As shown in FIG. 3, the battery pack 101 is accommodated within the battery pack compartment recess 103 formed on the rear wall 100d of the monitor apparatus 100 and the battery pack 101 is covered with a battery cover 104. As shown by an open arrow 120, the battery pack 101 is not exposed to the air unless the battery cover 104 is removed from the battery pack 101, and is affected by heat generated from an electric circuit (not shown) and the like within the monitor apparatus 100 as shown by solid arrows 121 in FIG. 3.
Under those circumstances, not only other cooling apparatus becomes necessary in order to hold the cells at proper temperature but also it becomes difficult to solve these problems because of various factors such as the weight of the information terminal apparatus, the trouble of wireless communication and the safety of the information terminal apparatus. In consequence, a disadvantage unavoidably arises, in which reduction of a time period in which the battery can be used is promoted (i.e., deterioration of battery).